Immersion Heater - PV electricity

[JohnBoyZ]

Mine has passed CE. It's not straightforward.

Well done!
Just out of interest which EU directives applied and was a notified body involved in the assessment?

EDIT: Sorry echase just to be clear, is it your filter that has CE marking or have you achieved CE for the whole of your controller as a commercial unit.

 

[Richard Walker]

Paul,

I'm in the same position as you can you let me know who you can get the 1 kw immersionheater from. I need an 18 inch one.

Thanks, I have found a company today that would be prepared to manafacture an element to whatever specification I need, for about £60 so I may go with that idea.

 

[pauldreed]

Paul,

I'm in the same position as you can you let me know who you can get the 1 kw immersionheater from. I need an 18 inch one.

Howden electro heating company

 

[KMSPaul]

Hello all. I've been reading the thread for a couple of days and there is some really interesting stuff here. I live up on the North York Moors, even further north than Paul, but still exporting despite now doing everything during daylight hours. I want to start heating my water as soon as I can. I' very comfortable with the micro option but the simplicity of the opamp/multiplier solution can't be ignored. I have a heat store from where water is pumped around radiators for heating,and it has a coil for heating the hot water. A gas boiler keeps the water at 75C. There is an immersion heater in the bottom of the tank for backup if the boiler fails. So I will be heating the whole tank to keep it at 75 rather than starting from cold.

As an aside, has anyone any experience with vanadium redox batteries or flow cells. These look very interesting for the future and well worth googling. With any luck their development will come on a pace now koenigsegg have put them in a sports car. In a few years we could be generating potential miles instead of hot water.

 

[echase]

Well done!
is it your filter that has CE marking or have you achieved CE for the whole of your controller QUOTE]

Whole contoller. All off the shelf filters should come CE marked

 

[stuart99]

Well done on this, are you now going to sell these?

 

[STOBBIE6]

New to thread though have read all 49 pages. must confess to being mechanical nor electrical.
Looking for help in simple terms, how do I measure whether I am importing or exporting as my solar PV is connected direct to consummer unit no henley block, not possible with 2CT's as they can't detect direction on flow.

 

[pauldreed]

Hi Stobbie, I'm afraid there is no simple answer, as most of the solutions are electrical.
If I were you, I would look towards OpenEnergyMonitor
I based my unit (and this thread) upon the work done by these very forward thinking Welsh guys, they are developing this apace.
You may wish to post in their forum and ask the same question.

 

[robassais]

I have often used equipment that sounds similar to what you are developing sourced from legrand. I worked for many years in France on domestic installations with only 15 and 20 amp supplys essentially to avoid constantly tripping the main fuse you fit a unit that would say turn off an emmersion when you put a kettle on etc etc I used legrand but am sure there are others

 

[Denmoz]

As a new PV'er, just had our 4kW system installed in Feb, I'm very interested in diverting any 'surplus power' into my hot water tank. I have already reduced the immersion heater to 1kW (there is also a timer which was already in the house) but would like to go further. Ideally to constantly compare generated power and consumed power (using CT's?), then to switch on the immersion automatically when there is 800W spare of generated power. I read your comments with much interest. I wondered, would you be kind enough to send me a system overview of what you have described and also a cost of the system described? As you mention I cannot seem to find an appropriate product on the market. I am originally an electrical engineer with HNC in Electrical & Electronic Engineering therefore wanting and able to create something but not to re-invent to wheel so to speak.

Many thanks
Dennis

For some time, since before coming across this thread, I have been designing an immersion controller for my 4kW PV system. I now have it finished and have built a few for family and friends. Seeing as the professional firms have not come up with a sensible product that is affordable please send me a private message if anyone wants to buy one. It is available as a kit or ready built. I am a Chartered Engineer so the design is hopefully quite professional but ultimately the risk is yours if you want to fit one.


It functions similar to the ones mentioned here, i.e. it controls the power into the immersion to ensure that export power is reduced to near zero (as long as the hot water is not up to temperature already). But it uses simpler components to reduce the cost and size, e.g. instead of an expensive PLC (Programmable Logic Controller) it has a small PCB that I make with a microprocessor and has less connections into the house electrics; this does not reduce its performance. It is designed for a 3kW or less immersion but would probably work up 10kW, although I have not tested that. Two or three 3kW immersions in parallel should be OK. It does not rely on an always on external PC either, which would burn lots of watts. No need to purchase an expensive <3kW immersion.

 

[methley]

I've been calibrating my system now for a few days, and I've noticed that when the tank is getting near "hot" that the immersion element power drops to roughly half of it's maximum rating. My immersion is a 3kW device, and when the tank gets nearly hot I can't get more than 1.5kW out of it, even with it powered full on.

Here's a typical plot. The blue line is excess power and the red is the feed to the immersion. As you see at the end of the curve the immersion thermostat turns off.

 

[TechyTim]

There are several simple controllers, like the SolarHeat controller I am marketing, which operate on PV output and a modulating one is being supplied with a monitoring system and PV panels by Engensa. I expect that others will be available later this year as Paul's colleagues on OpenEnergyMonitor seem to have cracked it. They all seem to use CT's or similar but the tricky bit is getting the switching or modulation right as reducing output by half reduces the heat by a quarter (IxIxR). Not much point in stopping the output to the grid if it doesn't actually do anything useful.

 

[shaunb]

Phew... all 50 pages took some reading. I was hoping to build one of these variable immersion controllers but something has just ocurred to me. In the near future I hope to install an Air Source Heat Pump. This will be primarily to supply heating but also Hot Water too. As Heat Pumps are purely electrical and perhaps most importantly have an efficiency around 300% I guess it makes no sense for me to build one of these to control an immersion heater? I suppose I should instead consider trying to control the heat pump's water heating circuit as that would be much more efficient? Although I guess the disadvantage is that the Heat Pump would either be on or off so I'd probably still end up importing power from the grid?

Anyone else on here got a heat pump and put any thought into this?
Thanks.

 

[echase]

I read your comments with much interest. I wondered, would you be kind enough to send me a system overview of what you have described and also a cost of the system described?
Many thanks
Dennis

I assume that was addressed to me. Please send me a Private Message.

 

[Denmoz]

Hi echase yes my comment was addressed to you I,m not sure how to send a private message, please could you reply to my private email at [email protected]. Then we can go from their.
Many thanks